The invention relates to the field of vehicle control and especially to the field of predictive vehicle control of a utility vehicle.
The rise in fossil fuel price and decrease of battery prices make electrified vehicles, such as hybrid and electric vehicles increasingly attractive. For a vehicle manufacturer it is important to offer a portfolio of powertrains used in these electrified vehicles. The powertrain design must match to customer requirements. For example the battery size of a small vehicle used in a transport network with concentrated charge pole placement can be designed smaller than the battery of a large vehicle used in a transport network with scatter charge pole placement. The consequence is a huge number of variants in the powertrain portfolio of the electrified vehicles.
Additionally, component properties, for example battery energy density, can change when a component is replaced. The consequence of all this is that a flexible and generic energy management strategy becomes very critical. There will simply not be possible to develop specific energy management algorithms for all possible variants in the powertrain portfolio of the electrified vehicles.
For vehicle customers, ownership cost is normally the important measure. This is especially valid for owners of heavy vehicles.
It is desirable to provide a method to control a vehicle and especially a utility vehicle, in order to minimise the ownership cost for an owner of the vehicle and especially a utility vehicle such as a truck.
The inventive method is applied upon a vehicle, which comprises a drivetrain, at least a first energy buffer and at least one auxiliary system. The invention uses the idea of a complete energy management and the use of at least an energy buffer within the vehicle in order to drive a vehicle from a first position to a second position in the most cost efficient way.
The result of the method is that a minimization of the ownership cost for a specific transport task of the vehicle and in the end for the whole lifetime of the vehicle can be performed. This is achieved through finding a balance between fuel consumption, grid electricity consumption (where applicable) and components wear and thereby minimise the total cost for propelling the vehicle. Grid electricity consumption is relevant for plug-in and full electric vehicles. The method recognises the cost for component wear, especially battery degradation, and take this into account when optimising the control of the vehicle. In the context of this invention, the ownership cost is the cost for propelling the vehicle from one position to another and at least including the energy needed for propulsion and wear on at least one critical component.
The inventive method is applicable on vehicle provided with at least a first energy buffer. An energy buffer can be any component that can store energy in any form, e.g. a pressure tank, an air conditioning system, any other thermal system of a vehicle, a flywheel and/or an electric battery.
To control the energy flows in the vehicle, the inventive method suggest that the vehicle is provided with a long term control and a short term control. The long term control is a process for setting a signal trajectory of at least one buffer parameter in the vehicle, during a predefined time horizon, i.e. how the at least one buffer parameter should vary over time during the predefine time horizon. The short term control thereafter controls the vehicle such that said signal trajectory is followed.
In order to achieve the long term control, the long term control;                accessing a momentary vehicle position and an upcoming travel route for the predefined time horizon, and        defining the at least one signal trajectory depending on at least the vehicle position and the upcoming travel route.        
In order to control the vehicle the short term control;                controlling the vehicle (v) such that the at least one buffer parameter follows said defined signal trajectory.        
Due to a complete vehicle approach considering both the vehicle powertrain and the vehicle auxiliary systems the planning of the use of the energy resources can be optimised. In the long term control at least one signal trajectory is set for at least one key vehicle parameter and in the short term control the vehicle is controlled such that the set signal trajectory is followed. The long term control becomes input about the environment in the form of position information and upcoming travel route information and also information about vehicle values. These are processed to an environment interpretation used for calculate the at least one signal trajectory. A complete vehicle value for a transport mission over said predefined horizon can be carried out in the most value efficient manner possible. That is, optimal in relation to both energy consumption and component wear.
The vehicle receives information about a vehicle position and an upcoming travel route for a predetermined time horizon. The information about the upcoming travel route at least comprises data about the topology of the travel route and optionally presence of a charging station along the upcoming travel route. A probable travel speed for the upcoming travel route can be calculated for the upcoming travel route.
A signal trajectory is a strategic control signal for a vehicle parameter. A typical signal trajectory is the state of charge of a battery, which varies over time, another typical signal trajectory is an on/off control of an engine.
In an aspect of the invention the long term control accessing information about the presence of a charging station and/or gas station at a predicted vehicle stop is included in the information given about the upcoming vehicle route. It is further provided that the long term control in addition or as alternative accessing, information about a distance to at least the next charging station and/or gas station along the upcoming travel route. By adding information to the long term control about where the vehicle can fill up/charge energy, the use of the energy already provided within the vehicle can be further optimised, in that a signal trajectory for the energy buffers can be set such that the battery is in need of a charge when arriving at a stop with a charging, station. Further a choice can be made between the use of stored energy, e.g. electrical energy, and fuel, e.g. using the combustion engine, in order to optimise the cost for driving the vehicle.
In an aspect of the invention the long term control is setting the signal trajectory at least further dependent on a battery cell temperature, an engine maximum power, a buffer maximum power and a buffer depth of discharge. By adding constraints to within which threshold values a predetermined number of parameters within the vehicle is allowed to vary, the setting of the at least one signal trajectory can be made more specific and the optimisation becomes more effective. Further, overload and high wear of components can be avoided. An example of a state that benefits from a constraint is the buffer state of charge. By setting lower and upper limitations, degradation of the energy buffer can be decreased.
The signal trajectory set is primarily an energy buffer signal trajectory, such as a state of charge. However, further signal trajectories can be set and be any one of an engine on-off control, an air condition power and an air compressor power. Further by providing a plurality of signal trajectories to be followed a more accurate cost optimisation can be achieved.
In one preferred aspect of the invention the long term control uses a complete vehicle cost optimisation in order to calculate the at least one signal trajectory. In this aspect the complete vehicle cost of a vehicle is at least dependent on a fuel consumption parameter and a buffer energy consumption parameter. Thereby can an optimal use of the energy provided in energy buffers be used in relation to the mostly more expensive energy from a combustion engine.
In a further preferred aspect, the complete vehicle cost optimisation is further dependent on at least one buffer wear parameter. A value is set on the buffer wear, whereby a cost for a predicted buffer wear for a specific signal trajectory can be calculated. The cost for the buffer wear can thereby be optimised together with the fuel consumption and the complete cost for taking the vehicle from A to B can be optimised. It is further preferred that the vehicle cost optimisation further is dependent on an energy consumption parameter, i.e. total energy consumption. Further component wear parameters can be integrated in the long term control such as mechanical brakes and other component subjected to wear. By including the wear of an energy buffer it can be controlled such that the wear of the buffer is minimised. For example when an upcoming travel route comprises a small downhill slope, no extra discharge of an electric battery, before reaching the downhill slope, is planned by the set signal trajectory, because the regeneration of energy during the small downhill is small. The regenerated energy can be used in other auxiliary systems which are not subjected to wear, such as an air conditioning system that can be driven by the regenerated energy.
The short term control controls the drivetrain and the auxiliary systems of the vehicle such that a cost for energy consumption of said vehicle is minimised, whereby said cost at least is dependent on the sum of energy losses (Ploss) in said vehicle, energy needed for the drivetrain and energy needed for auxiliary systems.
The short term control controls the drivetrain and said auxiliary systems such that a cost for energy consumption of said vehicle is minimised, wherein the cost at least is dependent on the energy losses in the vehicle, energy needed for the drivetrain and energy needed for auxiliary systems and thereby said signal trajectories are followed. The signal trajectories are set by the long, term control, in order to minimise the values decrease of the vehicle during a transport over the predefined time horizon. When the short term control controls the vehicle it optimises the use of energy in the vehicle in such a way that the set signal trajectories are followed.
The short term control controls at least one of an electric motor torque, a selection of gear speed, engine torque and air condition. The short term control preferably controls all aspects of the driveline and the auxiliary systems dependent on the signal trajectories set by the long term control.
The inventive method is preferably coded into a computer program comprising program code means for performing the steps of chosen aspects of the method when said program is run on a computer.
It is preferred that a computer readable medium carrying a computer program comprising program code means for performing the steps of the inventive method when said program product is run on a computer.
The method is preferably used in a utility vehicle. A utility vehicle will have the most benefit of the method due to its large mass. The invention therefore comprises a control unit for controlling a utility vehicle and the control unit being configured to perform chosen steps of the inventive method.